In order to efficiently utilize cellulosic resources, a method for efficiently decomposing cellulose has been explored in recent years. Cellulose is mainly decomposed by microorganism in nature, and it is known that various microorganisms such as bacteria and fungi produce cellulolytic enzymes.
These microorganisms secrete the cellulolytic enzymes outside those body, and cellulose is decomposed by its action into glucose via mainly cello-oligosaccharide and cellobiose. Cellulolytic enzymes are generally called as cellulase.
When cellulase is intended to artificially be produced, the genus Trichoderma is known as a microorganism secreting cellulase and is widely utilized. Moreover, a method for secreting cellulase by culturing the microorganisms classified under the genus Trichoderma using a culture medium containing nutrients such as carbon sources and nitrogen sources is also known.
However, in the conventional method for producing cellulase, materials usable as a carbon source are limited. For example, crystalline celluloses are expensive. Even if there are cellulosic resources which are inexpensive, they generally require pretreatments such as heat treatment or alkali treatment, and cause relatively high cost.
For example, Patent Literature 1 discloses a substrate for producing cellulase capable of inoculating cellulase-producing microorganisms by boiling used paper in a ferrous sulfate solution. In addition, Patent Literature 2 discloses a method for producing a substrate for producing cellulase capable of inoculating Trichoderma reesei which is cellulase-producing microorganisms by boiling finely-milled bagasse with caustic alkali and treating with a hypochlorite solution.
In addition, the cellulase obtained by these conventional methods mainly contains β-glucanase, has low xylanase activity, and is poor in ability to decompose a cellulosic resource containing xylan, such as bagasse and rice straw. Therefore, it is less effective for the purpose of efficiently utilizing naturally-occurring various cellulosic resources.
Patent Literature 3 discloses a method for producing xylanase by culturing a microorganism classified under the genus Trichoderma by using a diluted alcohol distillation waste fluid of rye subjected to preliminary treatment such as removal of solid constituents, concentration of nonvolatile components or autoclave treatment of the concentrate.
However, rye used as a carbon source in this technology is difficult to obtain, and it requires complicated pretreatment and causes high cost. In addition, production amount of β-glucanase even more decreases in this method.
Non Patent Literature 1 shows that productivity of cellulase is low in the test of enzyme production by Trichoderma reesei using paper (newspaper and office paper) which has not been subjected to pretreatment such as heat treatment or alkali treatment.
It has never been known a successful example which can highly produce β-glucanase and xylanase at the same time using paper which has not been subjected to heat treatment nor alkali treatment as a cellulosic resource.    [Patent Literature 1] Japanese Patent Laid-open Publication No. 2003-137901    [Patent Literature 2] Japanese Patent Publication No. H5 (1993)-33984    [Patent Literature 3] Japanese Patent Laid-open Publication No. H11 (1999)-113568    [Non Patent Literature 1] Applied Biochemistry and Biotechnology pp. 237-245, Vol. 84-86, 2000